1. Field of the Invention
The present invention relates generally to a. a cooling system to cool components of a computer tomography system arranged in a gantry housing. Moreover, the invention concerns a corresponding method to cool such components.
2. Description of the Related Art
In computer tomography systems, three-dimensional slice images of the inside of an examination subject are generated with the aid of an x-ray method. For this, two-dimensional x-ray slice images from which a three-dimensional slice image is reconstructed are generated by means of a scanning unit—generally called a gantry—which comprises an x-ray source (normally rotating around the acquisition subject) and an image acquisition system. The gantry is hereby typically located in a gantry housing which is annularly arranged around an examination subject acquisition space.
A fundamental problem in all x-ray systems is that 99% of the electrical energy used in the generation of the x-ray radiation in the x-ray source is transduced into heat energy. This heat that is incidental in the operation of the x-ray source must be dissipated in order to be able to operate over a longer period of time without overheating. This is in particular necessary when high x-ray capacities are required. As explained above, it is additionally aggravating in computer tomography systems that the x-ray source normally permanently rotates in the gantry housing around the examination subject acquisition space during a radiological acquisition. Due to this continuous rotation movement, the extremely high temperatures and the narrowness of the inner space of the gantry housing, the dissipation of the heat incidental in the operation of the x-ray source has proven to be complex and problematic.
The cooling systems previously used in such computer tomography systems normally comprise a plurality of heat exchangers that are installed inside the gantry housing. In order to dissipate the heat incidental on the rotating x-ray source from the gantry and from the inside of the gantry housing with optimal efficiency, conventionally a rotating heat exchanger is mounted in direct proximity to the x-ray source. This first heat exchanger delivers the heat to the air surrounding the gantry in the gantry housing. The heated air around the gantry can, for example, be cooled by a second heat exchanger which dissipates the heat acquired from the air to a cooling system outside of the gantry housing. German patent document DE 199 45 413 A1 shows a computer tomography system in which the second heat exchanger is thereby arranged stationary in the gantry housing relative to the x-ray radiator. The heat absorbed during the operation is dissipated via coolant lines (arranged in the second heat exchanger) to a cooling system outside of the gantry housing. German patent document DE 198 45 756 A1 offers an alternative. In the computer tomography system shown there, the second heat exchanger is arranged rotating in the gantry housing with the gantry. The dissipation of the heat ensues during the idle periods of the gantry between two measurements, in that the second heat exchanger is coupled by means of a fast coupling with a water cooling circuit arranged outside of the gantry housing.
It has proven to be disadvantageous in the cited cooling systems that a plurality of precise mechanical and electrical components are required that, due to their function, tend to wear out and must be correspondingly maintained. A further disadvantage is that the gantry housing must be correspondingly voluminously dimensioned based on the size of the required heat exchanger. Quite good cooling capacities can be achieved with a sufficiently large heat exchanger. However, it is disadvantageous that the cooling of the coolant is possible only given sufficient idle periods for the device. For the rest, the necessary coupling to an external coolant circuit complicates the assembly in which the gantry housing is positioned since a connection must be made between a stationary part of the computer tomography system such the parts can be pivoted.
It is desired so have such an assembly because by pivoting the gantry housing or, respectively, the gantry, a tilting of the image plane relative to the examination subject can be achieved in order to achieve, for example, a slice guide that is parallel to the subject surfaces. For example, arbitrary coronary slices can be created in this manner.